Carburetor



Feb. 5, 1963 J. L. SZWARGULSKI ET AL 3,0 76,639

CARBURETOR 5 Sheets-Sheet 1 OLIN. J. EICKMANN HAROLD A..CARLSON BY ALFRED C. KORTE AGENT Feb, 5, 1963 J. L. SZWARGULSKI ETAL 3, 7

CARBURETOR 5 Sheets-Sheet 2 Filed March 28, 1960 INVENTORS N i U E GNWUT T mw w m M MN SWAG L .DD JLE sN S L L JOHA Y B Feb. 5, 1963 Filed March 28, 1960 J. L. SZWARGULSKI ETAL CARBURETOR F IG.8.

Ill

5 Sheets-Sheet 4 INVENTORS JESSE LSZWARGULSK| OLIN J. EICKMANN HAROLD A. CARLSON B ALFRED C. KORTE AGENT Feb. 5, 1963 J. 1.. SZWARGULSKI ETAL 3,

CARBURETOR Filed March 28, 1960 5 Sheets-Sheet 5 F l G. l I

INVENTORS JESSE L. SZWARGULSKI OLIN J. EICKMANN HAROLD ACARLSON BY ALFRED C. KORT-E AGENT Unite States Patent 3,076,632 p 7 CARBURETOR;

Jesse L. Szwargiiiski, Florissant, Olin J. Eitlnnann, Normandy, Harold A. Carlson, v Brentwood, and AifredC. Korte, Jennings, Mos assignors to ACE Irrdusti'ies, llhcorporated New York, N.Y.,'a corporation of New Jersey Filed Mar. 28, 1960,.Scr. N 6 17,924

4-(Zlaims. (Cl. 261-64) This invention relates tocarbureto-rs for internal combustion engines, andparticularly to downdraftcarburetors useableon engines of automotive vehicles.-

Modern automotive vehicles have low hood lines with resultant intensification of heat around the carburetor in the engine compartment. The heat is further intensified in'manyinstances by the presence in the engine compartment of additional equipment for air conditioning and power steering. This boat undesirably tendsto prematurely volatilize fuel in the carburetor, and this tendency is aggravated by the increased volatility of modern fuels.

Accordingly, anobject of thisinvention is the provision of animproved construction for a carburetor which tends to reduce the effect of heat in the engine compartment on fuel in the carburetor, so as to reduce the tendency toward premature volatilization of fuel in the carburetor;

In general, a carburetor constructed in accordance with this invention comprises an assembly of sections, one of which constitutes afuelbowl section, formed to provide the fuel bowl of the carburetor, andanother of which constitutes a fuel system section. The latter has a portion extending down into the fuel bowl and has a fuel system, such as the high speed fuel system ofthe car'- buretor, embodied thereinr I As will appeanthis-fuel system section also has part of the idle fuel system and the accelerating fuel system of thecarburetor embodiedtherein. With this construction, the fuel system section may be isolated in such manner as to reduce the transfer of eattheretmandtoreduce the tendency toward premature volatilizat-ion of. fuel in the fuel systems embodiedin the fuel system section. In this respect, a further feature of the invention is the enclosure of the fuel system section between the fuel bowlsection and an airhorn section of the carburetor. v V

A further object of this inventionis the utilization of the cooling eifect of the expansion of fuel as it is introducedinto the stream of air flowing through the mixture conduit of the carburetor for keeping the fuel system temperaturesdo-wn,thereby further to reduce the tendency toward premature volatili zationofl fuel. Thisis accomplished by. making the; fuel system section of: a material ofv relatively high thermal conductivity. This effects reduction in temperature of the fuel. system section due to extraction of heat therefrom where it is subject to the cooling effect of the expansion. offuel.

A further objectof the invention, apart from the reductionof the effect of heat in. the engine compartment, is the provision of a carburetor oonstructionwhich has the advantage that one component thereof (the fuel system section) has the various fuel systems therein, and this one component may be pretestedprior to assembly with other component-sto check the functioning of'the fuel systems.

Other objects and featureswill be inpart apparent. and in-partpointed out hereinafter. i

3,076,639 Patented Feb. 5, 1553 The invention. accordingly comprises the constructions indicated; in the following: claims.

In the accompanying, drawings, in which severalv of various p-oss-ibleaembodiment's of the invention are illustrated;.

FIG. 1 isa schematic viewof a motor vehicle with a carburetor of this invention mounted thereon.

FIG. 2 is a view in elevation of thecarburetor of this invention, with the air filter removed.

3 is view in elevation of the carburetor of this inventionasviewedfro'm the left of FIG. 2.

PEG; 4 is a plan view of the carburetor of this invention with theair filter removed;

FIG. 5 is a plan view of the carburetor of this invention with the air horn casting removed and certain parts in section.

P16. 6 is a vertical section taken on line 66 of FIG. 4.

FIG. 7 is a vertical section takenon line 7-7 of FIG. 4, with parts broken. away.

. FIG; 8 is a vertical section taken on line 3-8 of FIG. 5'.

FIG. 9 is a bottom plan view of the carburetor of FIG. 3.

FIG. 10 is a vertical section taken on line 10-16 of FIG. 4.

FIG. 11 is a vertical section taken on line 1l--11 of FIG. 4.

FIG. 12' is a view in elevation of the carburetor as viewed from the right of FIG. 2 with the automatic choke cover cut away.

FIG; 13 is a sectional View taken on line 13-13 of FIG-2.-

FIG. 14 is a vertical section of a carburetor in accordance with: a modification of the invention.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring to the drawings, there is indicated at A in FIG. 1 an automotive vehicle having an engine E on which is mounted a carburetor C of this invention. Fuel is supplied to the carburetor C from the fuel tank T of the vehiclethrough a line L1 to a fuel pump P on the engine. Pump P may be operated by the engine and is adaptedto pump fuel to the carburetor through a line L2. The carburetor C is mounted on the intake manifold M of the engine. The exhaust manifold of the engine is indicated at H. An air filter F is conventionally mounted on the carburetor C.

Carburetor C (FIGS. 2, 3 and 6) is a single-bore downdraft carburetor, having a fuel bowl 1 and an adjacent vertical mixture conduit 3. Air is adapted to flow downwardly through mixture conduit 3 to intake manifold M of. engine 13' under control of a throttle-valve at the lower endof the mixture conduit. Fuel is adapted to be supplied to the mixture conduit from bowl 1 through fuel nozzle '7' foradmixture with the air to provide a combustiblemixture of air and fuel.

I As shown, the carburetor consists of an assembly of four individual sections which are designated S1, S2, S3 and S4. As shown best in FIG. 6, section S31 is a casting formed to providethe fuel bowl 1 and a portion 9 of mixture conduit 3, and may be referred to as the fuel bjowl section of the carburetor. The bottom of bowl 1 is stepped so that the bowl has a relatively deep generally rectangular part 11 adjacent to portion 9 of the mixture conduit 3 and a relatively shallow part 13 projecting outwardly from one of the long sides of the deep part 11. Portion 9 of the mixture conduit 3 is constituted by a vertical tubular portion integral with the bowl 1 on the other long side of part 11 of the bowl. The tubular portion 15 is of slightly conical form flaring downwardly to the lower end of portion 9 from an annular recess 17 at its upper end.

Section S2 is mounted on top of section S1. It comprises a casting formed to provide an upper portion 19 of the mixture conduit 3 and coextensive therewith. A portion 21 (FIGS. 2-6) forms a cover for bowl 1. A portion 23 of section S2 extends down from portion 21 into the bowl. Section S2 is cast from a material having good heat-conductive properties, such as aluminum and functions to conduct heat from the fuel bowl 1 to cooler portions of the casting, as described below. The bowl cover portion 21 of section S2 has essentially an inverted cup shape, with an outline corresponding to that of the fuel bowl 1. The mixture conduit portion 19 of section S2 is constituted by an annular formation integral with bowl cover 21 having a vertical axis and of rounded form convergent downwardly and merging with the upper end of tubular portion 15 of the mixture conduit. Portion 19 has a reduced-diameter lower end 27 fitting into recess 17. Conduit portions 19 and 15 form a venturi passage with the throat 22 of the venturi located at the level of the top of section S1.

Section S2 has cars such as indicated at 31 registering with cars 33 on section S1, which receive screws 35 for fastening section S2 on section S1. A gasket 37 is interposed between sections S2 and S1 and is made of a material such as a cellulose fiber mixed with a synthetic rubber binder, to thermally insulate section S2 from section S1.

Section S3 is a casting having a vertical tubular portion 39 which constitutes the air horn of the carburetor and a portion 41 of inverted cup shape overlying bowl cover 21 for enclosing certain parts to be described which extend upwardly above cover 21. Section S3, which may be referred to as the air horn section of the carburetor, is secured on top of section S2 by screws 43 which are threaded in tapped holes -55 in cover 21 and by screws 47 received in tapped holes 48 in cars 49 on mixture conduit portion 19 of section S2. A gasket 50 is interposed between sections S3 and S2. The gasket 50 is also made of a thermally insulating material such as a cellulose fiber with a synthetic rubber binder to heat insulate section S2 from S3. A screw-threaded socket 51 is provided at the top of the air horn 39 and coaxial therewith for attachment of the air filter F by a bolt 54-. This socket is supported by radial inclined struts 53; the struts and socket being cast integrally with the air horn S3.

Section S4 constitutes the throttle body of the carburetor, bottoming mixture conduit portion 9 of section S1. It has a cylindrical throttle bore 55 constituting a down- Ward extension of the mixture conduit 3, and horizontal flange portions 57 provided with holes 59 for receiving bolts 60 mounting the carburetor on intake manifold M. The throttle body S4 is fixed to the bottom of section S1 by long screws 63 which extend through sections S2 and S1 into tapped holes d1 in section S4. A thermally insulating gasket 65 made of an appropriate material such as a cellulose fiber mixed in a synthetic rubber binder, is interposed between sections S1 and S4. A throttle shaft 67 extends horizontally across the throttle bore 55 in the central vertical plane of the mixture conduit 3 and bowl 1. The throttle shaft 67 extends under the fuel bowl 1, which has a bottom formation such as indicated at 69 in FIG. 3 accommodating the shaft. A throttle valve 70 is secured on the throttle shaft in bore 55 at the lower end of the mixture conduit 3.

A combination fuel inlet fitting and needle valve body 71 (FIGS. 5 and 6) is threaded into a bushing 73 in the peripheral wall of the bowl cover 21 in the central vertical plane of the carburetor. Fitting 71 has a needle valve 75 horizontally slidable therein, and is formed to provide a seat 77 for the valve. Arms 79 pivoted on a horizontal rod 81 extending across the bowl cover 21 carry a yoke 33 having floats 35 at its ends. These fioats 85 are located in bowl 1 on opposite sides of downwardly extending portion 23 of section S2. The yoke has an upwardly extending central part 87 above the rod 81 engageable with the needle valve 75. The floats hold the needle valve closed when the fuel is at a predetermined level in the bowl such as indicated at L. When the fuel level drops, the yoke 83 swings downwardly so that part 87 rotates clockwise, as seen in FIG. 2 to permit the needle valve 75 to open and admit fuel to the bowl. Fuel flows into the bowl 1 until level L is restored and then the needle valve closes.

Section S2, part of which constitutes the bowl cover 21 and part of which constitutes the upper portion 19 of the mixture conduit 3, has embodied therein the entire high speed fuel system 91 of the carburetor. This is the system for supplying fuel from bowl 1 to mixture conduit 3 at engine speeds above idle. This high speed system includes means for metering the fuel to provide different air to fuel ratios. Section S2 also contains the idle fuel system of the carburetor which is the system for supplying fuel from the bowl 1 to the mixture conduit 3 when the engine is idling. An accelerating fuel system for the carburetor is also contained in section S2. The accelerating fuel system is for pumping fuel from the bowl to the mixture conduit upon acceleration. Thus, section S2 may be referred to as the fuel system section or cluster of the carburetor. It is in effect sandwiched between section S3, the air horn section and section S1, the fuel bowl section.

The high speed fuel system includes an arm 97 cast integrally with section S2, and extending radially into the mixture conduit 3. Arm 97 contains a primary venturi 99 at its outer end coaxial with the adjacent mixture conduit portion 19. The bowl cover 21 is formed with an inclined portion 101 providing a recess 103 to enable a downwardly inclined passage 105 to be drilled in section S2 through the arm 97 to the primary venturi 99. The upper end of passage 105 is closed by a plug 103, and a nozzle tube 111 is provided in the lower end of passage 105 projecting into the primary venturi 99. The nozzle tube 111 has a press fit in passage 105. The arm 97 with primary venturi 92 thereon and tube 111 constitute the nozzle 7 of the carburetor.

Portion 23 of section S2 extends downwardly from the bowl cover 21 into the fuel bowl 1 closely adjacent to the mixture conduit 3. Portion 23 is in effect suspended in the bowl so that it extends down nearly to the bottom of the deep part 11 of the bowl and is spaced from all portions of the wall of the fuel bowl 1. This may be referred to as a block and is formed with a vertical cylindrical recess 115. The axis of this recess 115 is slightly offset to the right of the central plane of the carburetor as viewed in FIG. 6. A vertical passage 117 of smaller diameter than recess 115 extends between the upper end of recess 115 and the fuel passage 195. This passage 117 is centered in the central plane of the carburetor. A main fuel tube 119 has its upper end press fitted into passage 117 and extends downwardly into recess 115. The bottom of the recess 115 is sealed by a plug 121.

Section S2 is provided with a vertical hole 123 (see FIG. 7) extending down from its top through block 23 to a recess 125 of larger diameter than hole 123. This recess 125 extends up from the bottom of block 23. A fuel metering rod 127 is vertically slidable in the hole 123 and has a stepped lower end portion 129 (two steps being shown) cooperable with an annular fuel metering jet 131 held in a counterbore at the lower end of recess 125. An inclined cross-passage 133 (see FIG. ii) in portion 23 intersects recess 125 and extends to; the recess 115 adjacent the lower end of. the fuel tube.119. The outer end of cross-passage 1334s closed by plug 13-5.' Fuel is adapted to flowfr'orn the bowll through-metering jet 131 to recess 125,- thence through inclined cross-passage 133 to recess 115 which constitutes a fuel well, thence upward through the main fuel tube 119 and passage 117 to the fuel passage 105 anddown the latter and out through the nozzle tube 111 into the mixture conduit 3 for admixture with air flowing downwardly through the mixture conduit. Metering rod 127 :is adapted to controlthe rate of flow, according to the position of its lower end portion 129 in the orifice in jet 131'.

Section S2 is formed with acylindrical recess 137 adjacent to metering rod hole 123 extending down and'penetnating into but terminating short of' the lower end of block portion 23. This recess 137constituts a cylind'er for a metering r-od piston 139, the latter being slidable up and down in the recess of cylinder-137 andextending upwardly above the" top of section S2. The piston 139 is biased upwardly by a'spring 1'40 positioned betweenlthe bottom of" cylinder 137 and piston 139. Piston 139is adapted to move downwardly under the influence of vacuum in the lower part of cylinder 137transmitted thereto from mixtureconduit 3 below the throttle valve 5' via a vacuum passage 143 drilled in block 23 and intersecting the lower end of the cylinder 137; which is otherwise closed. The inner end of passage 143intersects the lower end of a long inclined passage 145 '(FIG. 8) drilled down from a recess 147 in the top of section 82 When the carburetor sections are assembled, this recess. 147 is closed by, gasket 50/ between sections S2 and S3. An oppositely inclined passage 149 extends down from recess 1'47through section S2 'to the upper end of a vertical passage 151 in mixture conduit portion 9 of'section S1.

Passage 151' extends down to the upper end of a vertical passage 153 in throttle body section S4, and there is a vacuum port 155' (FIGS. 8 and'9) providing for communication between the throttle bore 55 and the lower end of passage 153;

The upper end of metering rod piston 139 and the upper end of the metering rod. 127 are interconnected by a bar 157. Block 23 has a recess or passage 159 providing communication from the bowl 1 to the metering rod hole 123-above the recess 125 and the cross-passage 133. Fuel in this recess or pass-ageil59, which is partly below and partlyabove fuel level L, provides an air seal on the metering rod to prevent leakage of air pastrod .127 to recess 125.

The idlefuel system comprises an idle tube. 161 (see FIG. which extends downwardly intofuel well 115 from a vertical passage 163 through the upper surf-ace of section S2. The air horn section S3 has a horizontal rib 165 (FIGS. 4, 10, 11) in which a horizontal passage 167 is drilled to an intersection with a vertical passage 169 in section 53 which registers. with passage 163. The outer end ofpassage167. is closed by "a plug 170'after insertion of an eeonomizer restriction 171 in passage 167. Section S3 is providedwith a vertical hole 173 extendingdown from passage'167 betweenplug170 and'economizer 171 to'a groove 1'75'(F1GS. 4 audio) in the top o-fsectionSZ. Aninclined ho'le'177 extends up from the bottom of section S2 to an intersection with groove 175. Hole 177 registers with vertical hole 179 extending through the mixture conduit portion. 90f section S1, and hole 179 registe rs with an idle port recess 181 in the top of the throttle body sect-ionS t. An idle .by-pa'ss 183 extends from hole 179 in portion 9 of section S1 to the mix- :ture conduit 3 adjacent the lower end'of portion 9, and an idle port 185 provides for communication from recess 181 into the throttle bore 55. There is an idle bleed 189 in rib 165' for bleeding air into the idle system between idle tube 16-1 and economizer 171. An idle adjusting is sucked. into the intake manifold M through the idle port 193. This mixture is formed from air passing into the idle port recess181 from idle bleed 189, idle by-pass 183 and idle port 185. Idle fuelis sucked up from fuel well I15'through the idle tube 161 into the idle passage 167 and 179 where it mixes with idle air. The idle air and fuel mixture flows into the idle system because of the low manifold pressure present in recess 181.

The accelerating fuel system (FIG. 11) comprisesa pump including an inverted cup shaped pump piston 197 slidable in a Vertical cylindricalrecess 199 formed in block 23. This cylindrical recess 199 extends up from the bottom of the right side of block 23, as viewedin FIG. 5, and is open at the bottornat 2th). to the fuel bowl. A check valve disc 201 extends across the inside of piston 197, and forms an inlet check for the space in cylinder 199 above the piston. Check valve 201 opens for priming the cylinder and closes on upward movement of'thc piston 197. The piston is biased upwardly by a spring 203 from the bottom of bowl section 11. Piston 197. has a rod 205 extending upwardly therefrom and slidable in vertical hole 2G7 in section S2. Packing for rod 295 is indicated at 209. Section S2 is formed with a pump outs let passage 211 leadingfrom the upper endof the cylindrical recess 199 to a recess 212? in the top of casting S2 which in turn leads through a restriction or pump jet 213 into another pocket 215 in the top of section S2. This pocket is open at the top to mixture conduit 3 and in lateral communication with the mixture conduit via a lateral port 217. Between passage 211 and recess 212 there is a discharge valve 219 for checking flow of fuel back into passage 211;

The pump piston 197 isadapted to be held down against the upward bias of pump spring2tl3 by a pump'actuating arnr221 fixed-to the upper end of a pump-actuating rod 223 slidable vertically in a bore 225 formed in section S2 alongside the pump cylinder199. This actuating arm 221 extends over the upper end of piston rod 2115. Rod 223 extends down below the fuel bowl section S1 through an opening 226 in section S1. Throttle shaft 67 has a crank arm 227 (FIGS. 3 and 11) fixed on its end under the fuel bowl 1; S-sh'aped link 229 interconnects this crank arm 27' and the lower end of rod 223. When the throttle shaft 67 turns inthrottle-opening direction, rod 223 is driven upward, thereby raising arm 221 to permit spring 203 to drive pump piston 197 upward through a discharge stroke. A limited amount of fuel is thus forcedalong passage 211,.past valve 219 and through jet 213 and passage 217 out intothe mixture conduit 3. This instantaneously enriches the fuel mixture passing through the carburetor and provides sudden acceleration responsive to the action of the throttle opening.

When the throttle shaft turns in throttle-closing direction, link 229 pulls rod 223 down, and arm 221 on rod 223 pushes the pump piston down which opens valve 291 to allow fuel to fill the pump cylinder199. The throttle shaft is biased to turn in throttlerclosing direction by a spring 231. The upper ends of rods 205 and $223 and arm 221 are enclosed within portion 41 of section 53'.

A choke shaft 233 (see FIGS. 6 and 7) extendsacross theair horn 39 parallel to the throttle shaft'67, and offset from the vertical plane of the throttle shaft as appears in FIG. 4. A choke valve 235 is unsymmetrically secured on the choke shaft in the air horn section S3 and unbalanced to: openunder the bias of gravity and air flowing downwardly through'the air born 39. Thexchoke shaft extends through a bearing 237'cast integrallywith the 'air horn 39 and into a cup-shaped casing 239 east integrally as a part of air horn section S3. It is closed by acupshaped dust cover 241 containing a choke thermostatic coii 243 (FIGS. 6 and 13). Cover 241is rotatable on casing'2 39, clamping members 245 and clamp screws 24) being provided fo r clamping the cover in various P681: tions of angular'adjustment relative to the casing. A pars earnest) tition or baffle plate 249 is provided between the casing and the cover.

A choke lever 251 (FIG. 12) is fastened on the end of the choke shaft 233 in casing 239. This lever has radial arms 253 and 255, a finger 25'? extending laterally from arm 255, and a finger 25'3 extending at right angles to finger 257 outward of the end of the choke shaft. Arm 253 is interconnected by a link 259 with a vacuumresponsive choke piston 261 slidable in a vertical chokc cylinder 263 formed as a part of casing 239. The lower end of cylinder 263 is closed by a plug 265. The space in cylinder 2.63 below piston 261 is in communication with mixture conduit 3 below the throttle valve 7% via passages in sections S3, S2, S1 and S4 indicated at 2&7 in FIGS. 6 and 12. Choke cylinder 263 has longitudinal scores such as indicated at 269. The arrangement is such that piston 261 is adapted to move downward under the influence of vacuum in the lower end of cylinder 263 to swing the choke valve open.

The cover 241 has a center stud 271 with the inner end of thermostatic coil 243 being secured to this stud. The coil 243 has a hook 273 at its outer end which engages the finger 257 of choke lever 251, this finger extending through an arcuate slot 275 in partition 249. Coil 24-3 acts as a spring tending to close the choke valve 235. When heated, coil 243 relaxes to permit the choke valve to open. Casing 23s has a hot air inlet 277 and a passage 279 from this inlet to a hole 231 (FIG. 13) in partition 249. Air is delivered to inlet 277 via a tube 233 from a heat pocket in the exhaust manifold H of the engine to operate coil 243 to release the choke valve 235.

A throttle arm 2S5 (FIGS. 2, 6 and 12) is fastened on the end of throttle shaft 67 under the choke casing 23-) and cover 241. This arm has a finger 287 engageable With a stop screw 289 adjustably threaded in a lug 2&1

on throttle body S4 to determine the fully closed position of the throttle valve. A fast idle cam 293 is rotatably mounted on the end portion of choke shaft 233 on the inside of choke lever 251. A spring 295 bigses the fast idle cam to rotate clockwise as viewed in FIG. 12 relative to the choke shaft 233 and choke lever 251. This spring 295 has one end 2&7 hooked around the arm 255 and its other end 299 hooked around a projection 301 on the fast idle cam. A bar 303 is slidably mounted in a vertical guide slot 3435 in choke casing 259 and has a shoulder 3W (FIG. 6) engageable with the fast idle cam 2%. A link 309 interconnects throttle arm 235 and the lower end of bar 393, so that bar 3% is pulled down when the throttle valve 5 is opened, and pushed up when the throttle valve is moved in closing direction. Bar 3% has an unloading finger 311 at its upper end engageable with finger 258 of choke lever 251 when bar 3&3 is moved downward on full opening of the throttle valve to open the choke valve for unloading purposes.

The fuel bowl 1 is vented into the mixture conduit 3 via passages 313 in sections S2 and S3 (see FIGS. 6 and 13). The fuel well 115 is also vented to the mixture conduit 3 via a passage 315 (FIG. 6). Pump actuating arm 221 has a finger 3T7 (FIGS. 2, 6 and 7) which extends under bar 157. When the throttle valve 5 is opened wide, and rod 223 is moved upward to its upper limit of travel, finger 317 is adapted to lift metering rod 127 upwardly for increased fuel flow irrespective of vacuum acting on metering rod piston 132.

in the operation of the carburetor, fuel for high speed operation of the engine (throttle valve 7t? open) is delivered from the bowl 1 through the orifice in metering jet 131 at a rate dependent upon the position of metering rod 127 to recess 125' (see FIG. 7), thence through cross-passages 133 to the fuel Well 115, thence up through main fuel tube 119 to passage 1.85 (see FIG. 10), and thence out through nozzle 7 into mixture conduit 3. The ,position of metering rod 127 depends on vacuum in cylinder 137 below metering rod piston 139, the rod being up when vacuum is low for increased. fuel flow, and being down when vacuum is high for decreased fuel flow. Fuel for idling (throttle valve 70 closed or almost closed as determined by the fast idle cam 2%) is delivered from fuel well via idle tube 161 and the idle system passaging through idle port and idle adjustment screw port 193 to the mixture conduit 3. On opening of the throttle valve 70, pump piston 197 is driven upward by pump spring 293 to pump accelerating fuel to the mixture conduit.

The fuel system section S2 of the carburetor, being sandwiched or enclosed between the fuel bowl section S1 and the air horn section S3, has little surface area directly exposed to heat in the engine compartment of the vehicle, and is insulated against conduction of heat thereinto from sections S1 and S3 by gaskets 37 and 5B. This reduces the effect of engine compartment heat on section S2, and reduces the tendency toward premature volatilization of fuel in the fuel passages of the high speed fuel system, the idle fuel system and the accelerating fuel system, which are provided in the block 23 of section S2.

Expansion of fuel as it exits from nozzle 7 into the mixture conduit 3 has a cooling effect on nozzle 7. Accordingly, there is an extraction of heat from section S2 by heat being transferred from the nozzle to the expanding fuel in conduit 3. During engine operation, there is a conductive flow of heat through the metallic casting S2 from those portions of casting S2 submerged in the fuel of bowl 1 to the cooler nozzle section 7 and venturi portion 99. The fuel in bowl 1, also, has a heat insulating effect on the fuel systems block 23 submerged therein. This all reduces the elfect of engine compartment heat during operation of the vehicle, and also when the engine stops, section S2 tends to be cooler than section S1 and S3.

A significant feature of the construction is that the entrances to all three fuel systems are low in the bowl. Thus, even though the fuel level in the bowl should be lowered by volatilization of fuel under unusual conditions, it is unlikely that the level would drop below the fuel system entrances. Thus, the fuel level in the bowl generally remains sufiiciently high, even after a so-called soak, i.e., a short period (fifteen minutes), during which the engine is stopped after a hard, hot run. Accordingly, difficulty in starting after such a soak is avoided because of the presence of liquid fuel in the several systems rather than fuel vapors.

Another significant feature of the construction is that the fuel system section S2 can be pretested by itself prior to assembly with the other sections for checking its fuel metering performance and the operation of the accelerating pump. This eliminates the necessity of assembling carburetor components prior to testing required by prior constructions, as, for example, where the fuel well is in the fuel bowl section.

FIG. 14 illustrates a modification wherein the nozzle passage, designated 105a to distinguish it from passage 105 of FIG. 10, is an uphill instead of downhill passage. In this modification, a passage 321 may be provided in the fuel system section S2 interconnecting the space within the dust cover 41 of air horn section S3 and the mixture conduit to equalize the pressure under cover 41. In other respects, the FIG. 17 modification is the same as the embodiment of the carburetor shown in FIGS. 2-16.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions Without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. A carburetor comprising a first integral structure forming a fuel bowl and a mixture conduit with a vertical axis, a. separate second integral structure fitted to the top of said first integral structure, said second structure having a first portion forming a cover over said fuel bowl and a venturi section'coexten'siv'e with said mixture conduit, a thirdseparate structure fitted to the top of said second structure and-forming aninlet air passage to said carburetor and coextensive with said mixture conduit and venturi section, afirstthermally insulating gasket between said first and second integral structure and a second thermally insulating gasket between said second and third section to thermally insulate said sections one from the other, afourth integral structure fitted to the bottom of saidfirstsection and including a bore forming an extension of said-mixture conduit, a'throttle shaft extending through saidbore and a throttle valve within said bore and fixedto said throttleshaft to control flow of air and-fuel therethrough,- saidsecond structure having a second integral portionthereof depending into said fuel bowl from said first cover portion and having a plurality of terminal end portions positioned adjacent to the bottom of said fuel bowl and a first fuel passage including a fuel well extending from one of said terminal end portions through said second structure to said venturi section, an apertured fuel jet mounted in said first fuel passage, a fuel nozzle in said first fuel passage opening into said venturi section, said second structure having a second fuel passage extending from another one of said plurality of terminal end portions to said venturi section, an accelerating fuel pump piston within said second fuel passage, a spring between the bottom of said fuel bowl and said piston for biasing said piston upwardly in a pumping direction, an operating linkage connected between said throttle and said piston and supported by said second structure to move said piston downwardly against said spring bias.

2. A carburetor comprising a first integral structure forming a fuel bowl and a mixture conduit with a vertical axis, a separate second integral structure fitted to the top of said first integral structure, said second structure having a first portion forming a cover over said fuel bowl and a venturi section coextensive with said mixture conduit, a third separate structure fitted to the top of said second structure and forming an inlet air passage to said carburetor and coextensive with said mixture conduit and venturi section, a first thermally insulating gasket between said first and second integral structure and a second thermally insulating gasket between said second and third section to thermally insulate said sections one from the other, a fourth integral structure fitted to the bottom of said first section and including a bore forming an extension of said mixture conduit, a throttle shaft extending through said bore and a throttle valve within said bore and fixed to said throttle shaft to control flow of air and fuel therethrough, said second structure having a second integral portion thereof dependinginto said fuel bowl from said first cover portion with an end terminating adjacent to the bottom of said fuel bowl and a first fuel passage including a fuel well extending from said terminal end through said second structure to said venturi section, an apertured fuel jet mounted in said first fuel passage, a fuel nozzle in said first fuel passage opening into said venturi section, said second structure having a second fuel passage extending from said fuel well upwardly to a first aperture in said second gasket, said third structure formed with a first conduit connected with said aperture and extending horizontally to a second aperture in said second gasket, said first, second, third and fourth structures forming a second conduit connecting said second aperture to a port opening into said mixture conduit adjacent to said throttle valve, and a gas pressure responsive means mounted on said second structure and including a metering rod having a calibrated end extending through said fuel jet for varying the fuel flow through said fuel jet, said first, second and fourth structures having a third passage extending i0 fromtsaid pressure responsive meansto said mixture conduitc 3. A carburetor comprising a first integral structure forminga fuel bowl and a mixture conduit with a vertical axis, a separate second integral structure fitted to the topof said first integral structure, saidlsecond structure havinga. firstportion forming acover over said fuel bowl and a venturisection. coextensive with said mixture conduit, a third separate structure fitted to thetop of said second structure and forming an inlet air passage to said carburetor and coextensive with said mixture. conduit and venturi section,a-first-thermally insulating gasket between said first and secondintegral structureand a second then' mally insulating gasket between said second and third section to thermally insulate saidsections one from the other, a fourth integralstructure fitted'to the bottom of said first section and including a bore forming an extension of said mixture conduit, a throttle shaft extending through said bore and a throttle valve within said bore and fixed to said throttle shaft to control flow of air and fuel therethrough, said second structure having a second integral portion thereof depending into said fuel bowl from said first cover portion and having a plurality of terminal end portions positioned adjacent to the bottom of said fuel bowl and a first fuel passage including a fuel Well extending from one of said terminal end portions through said second structure to said venturi section, an apertured fuel jet mounted in said first fuel passage, a fuel nozzle in said first fuel passage opening into said venturi section, said second structure having a second fuel passage extending from another one of said plurality of terminal end portions to said venturi section, an accelerating fuel pump piston within said second fuel passage, a spring between the bottom of said fuel bowl and said piston for biasing said piston upwardly in a pumping direction, an operating linkage connected between said throttle and said piston and supported by said second structure to move said piston downwardly against said spring bias, and gas pressure responsive means mounted on said second structure and including a metering rod having a calibrated end extending through said fuel jet for varying the fuel flow through said fuel jet, said first, second and fourth structures having a third passage extending from said pressure responsive means to Said fuel conduit and a fourth idle mixture passage extending from said fuel well to said mixture conduit adjacent to said throttle valve.

4. A carburetor comprising a first integral structure forming a fuel bowl and a mixture conduit with a vertical axis, a separate second integral structure fitted to the top of said first integral structure, Said second structure having a first portion forming a cover over said fuel bowl and a venturi section coextensive with said mixture conduit, a third separate structure fitted to the top of said second structure and forming an inlet air passage to said carburetor and coextensive with said mixture conduit and venturi section, a first thermally insulating gasket between said first and second integral structure and a second thermally insulating gasket between said second and third section to thermally insulate said sections one from the other, a fourth integral structure fitted to the bottom of said first section and including a bore forming an extension of said mixture conduit, a throttle shaft extending through said bore and a throttle valve within said bore and fixed to said throttle shaft to control flow of air and fuel therethrough, said second structure having a second integral block portion thereof depending into said fuel bowl from said first cover portion and having a plurality of terminal end portions positioned adjacent to the bottom of said fuel bowl, said block formed with a first fuel passage including a fuel well extending from one of said terminal end portions through said second structure to said venturi section, an apertured fuel jet fixed in said first fuel passage at said one terminal end portion, a fuel nozzle in said first fuel passage opening into said venturi section, said block having a second fuel passage formed therein and extending from another one of said plurality of terminal end portions to said venturi section, an accelerating fuel means including a pump piston supported in said block within said second fuel passage, a spring between the bottom of said fuel bowl and said piston for biasing said piston upwardly in a pumping direction, an operating linkage connected between said throttle and said piston and supported by said second structure to move said piston downwardly against said spring bias, and a gas pressure responsive means operatively fitted in said bl cl; and including a metering rod having a calibrated end extending through said fuel jet for varying the fuel flow through said fuel jet, said first, second and fourth structures having a third passage extending from said pressure responsive means to said mixture conduit.

References Cited in the file of this patent UNITED STATES PATENTS Bracke June 13, 1939 Bal Aug. 25, 1942 Stupecky Apr. 18, 1944 Mosely et al. July 2, 1946 Bicknell Nov. 5, 1946 Scott Sept. 2, 1952 Olson May 26, 1953 Olson et al Nov. 20, 1956 Kittley et a1 Oct. 14, 1958 Gretz Mar. 3, 1959 Brown et al. Jan. 12, 1960 Csecs July 5, 1960 Carlson Mar. 28, 1961 Brown et al. Aug. 8, 1961 

1. A CARBURETOR COMPRISING A FIRST INTEGRAL STRUCTURE FORMING A FUEL BOWL AND A MIXTURE CONDUIT WITH A VERTICAL AXIS, A SEPARATE SECOND INTEGRAL STRUCTURE FITTED TO THE TOP OF SAID FIRST INTEGRAL STRUCTURE, SAID SECOND STRUCTURE HAVING A FIRST PORTION FORMING A COVER OVER SAID FUEL BOWL AND A VENTURI SECTION COEXTENSIVE WITH SAID MIXTURE CONDUIT, A THIRD SEPARATE STRUCTURE FITTED TO THE TOP OF SAID SECOND STRUCTURE AND FORMING AN INLET AIR PASSAGE TO SAID CARBURETOR AND COEXTENSIVE WITH SAID MIXTURE CONDUIT AND VENTURI SECTION, A FIRST THERMALLY INSULATING GASKET BETWEEN SAID FIRST AND SECOND INTEGRAL STRUCTURE AND A SECOND THERMALLY INSULATING GASKET BETWEEN SAID SECOND AND THIRD SECTION TO THERMALLY INSULATE SAID SECTIONS ONE FROM THE OTHER, A FOURTH INTEGRAL STRUCTURE FITTED TO THE BOTTOM OF SAID FIRST SECTION AND INCLUDING A BORE FORMING AN EXTENSION OF SAID MIXTURE CONDUIT, A THROTTLE SHAFT EXTENDING THROUGH SAID BORE AND A THROTTLE VALVE WITHIN SAID BORE AND FIXED TO SAID THROTTLE SHAFT TO CONTROL FLOW OF AIR AND FUEL THERETHROUGH, SAID SECOND STRUCTURE HAVING A SECOND INTEGRAL PORTION THEREOF DEPENDING INTO SAID FUEL BOWL FROM SAID FIRST COVER PORTION AND HAVING A PLURALITY OF TERMINAL END PORTIONS POSITIONED ADJACENT TO THE BOTTOM OF SAID FUEL BOWL AND A FIRST FUEL PASSAGE INCLUDING A FUEL WELL EXTENDING FROM ONE OF SAID TERMINAL END PORTIONS THROUGH SAID SECOND STRUCTURE TO SAID VENTURI SECTION, AN APERTURED FUEL JET MOUNTED IN SAID FIRST FUEL PASSAGE, A FUEL NOZZLE IN SAID FIRST FUEL PASSAGE OPENING INTO SAID VENTURI SECTION, SAID SECOND STRUCTURE HAVING A SECOND FUEL PASSAGE EXTENDING FROM ANOTHER ONE OF SAID PLURALITY OF TERMINAL END PORTIONS TO SAID VENTURI SECTION, AN ACCELERATING FUEL PUMP PISTON WITHIN SAID SECOND FUEL PASSAGE, A SPRING BETWEEN THE BOTTOM OF SAID FUEL BOWL AND SAID PISTON FOR BIASING SAID PISTON UPWARDLY IN A PUMPING DIRECTION, AN OPERATING LINKAGE CONNECTED BETWEEN SAID THROTTLE AND SAID PISTON AND SUPPORTED BY SAID SECOND STRUCTURE TO MOVE SAID PISTON DOWNWARDLY AGAINST SAID SPRING BIAS. 